漸層 刮板

點刮
PImage imgBG;
PImage imgBlack;
void setup() {
  size(800, 600);
  imgBG=loadImage("imgBG.jpg");
  imgBlack=createImage(800, 600, ARGB);
  imgBlack.loadPixels();
  for (int i=0; i<imgBlack.pixels.length; i++) {
    imgBlack.pixels[i] = color(0, 0, 0, 255);
  }
  imgBlack.updatePixels();
}
void draw() {
  image(imgBG, 0, 0, width, height);
  image(imgBlack, 0, 0, width, height);
}
void mouseDragged() {
  imgBlack.loadPixels();
  imgBlack.pixels[mouseX+mouseY*width] = color(0, 0, 0, 0);

  imgBlack.updatePixels();
}

void setup() {
  size(800, 600);
  colorMode(HSB, 800);
  background(0);
  strokeWeight(2);
}
void draw() {
  if (mousePressed) {
    stroke(mouseX, mouseY, 800);
    line(mouseX, mouseY, pmouseX, pmouseY);
  }
}